Related Stories

From helping the Hubble Space Telescope peer back into time, to understanding osteoporosis in humans, space shuttle crews perform important research, scientists say.

The immediate benefit of some experiments conducted on shuttles - and the International Space Station they help build - may not always be obvious. But they can shed light on a range of everyday problems on Earth, and help us understand the vast reaches beyond, they said.

Seven astronauts died on Saturday when the space shuttle Columbia broke up over Texas as it came in for a landing in Florida, in the United States. NASA has grounded the three remaining shuttles until the cause of the disaster is found and corrected.

Some critics have called for an end to the shuttle program, saying it is not worth the risks and expense. But David Akin, an associate professor of aerospace engineering at the University of Maryland, argues that space exploration is an investment in the future of humanity.

"If you plant a field, the first thing you do when you harvest is you set aside seed for next year," he said. "Basic research of any kind really is the seed corn for the future."

The shuttles, designed as a way of getting in and out of space quickly, have not only helped build and re-supply the space station, but have been key to maintaining the Hubble telescope which, orbiting above the blurring effects of the Earth's atmosphere, can look back in space and time to virtually the birth of the universe.

In 1999, Columbia also launched Chandra, an orbiting X-ray observatory that has been used to peer at black holes, probe the structure of our own Milky Way galaxy and find other galaxies in seemingly empty patches of sky. "That again was a massive satellite and probably never would have been lifted without the shuttle's lift capacity," said Stockman.

Observations by the Hubble and other instruments do more than provide interesting pictures, Akin said. "If there is any central question to existence, it's where do we come from, where did the universe come from, what are we doing here and where are we going," he said.

Shuttle missions have also provided answers with immediate impact on Earth, including causes and possible cures for osteoporosis. "In astronauts, when their skeletal system no longer has to work against the force of gravity, the body says, 'Hey, I don't need all these bones,' and it starts sucking calcium out of the bones," Akin said.

Dr Felicia Cosman, clinical director at the National Osteoporosis Foundation in the United States, and a specialist in the bone-thinning disease, said the weightlessness of space provides a perfect laboratory.

"It is a great model for what happens with immobilisation due to any disease," she said. "I think we can use the information to try and figure out how to use mechanical devices to actually build bone and to better design agents for future osteoporosis treatment."

Shuttle astronauts have also used their own bodies as laboratories to study muscle wasting. Astronauts lose muscle mass in the almost zero gravity environment above Earth, and studying this process not only helps future space travelers but also people with similar conditions on Earth - including the aged and people with severe burns.

One shuttle mission mapped the entire Earth in a few days, Akin said, "more or less [making] every form of mapping obsolete," Akin said. "We have never been able to map accurately in height and not to that resolution."

Apart from a multitude of civilain everyday uses, they can have an impact on issues at the top of the political agenda, he added: "If you happen to want to send cruise missiles against someone you don't like, that's also useful."

While the U.S. military has acknowledged funding military research in connection with the shuttle program, much of that research is classified. The Pentagon has also used shuttle flights to lift satellites, including spy satellites critical to modern warfare, into space.

Shuttle-based mappers have also made a detailed radar map of Earth, said Roald Sagdeev, a physicist at the University of Maryland who once headed the former Soviet Union's space research effort. "We can have a three-dimensional map of the Earth," he said.